research article a study on control strategy of...
Post on 01-Apr-2020
0 Views
Preview:
TRANSCRIPT
Hindawi Publishing CorporationMathematical Problems in EngineeringVolume 2013, Article ID 208753, 9 pageshttp://dx.doi.org/10.1155/2013/208753
Research ArticleA Study on Control Strategy of Regenerative Braking inthe Hydraulic Hybrid Vehicle Based on ECE Regulations
Tao Liu, Jincheng Zheng, Yongmao Su, and Jinghui Zhao
School of Automobile Engineering, Harbin Institute of Technology, Weihai 264209, China
Correspondence should be addressed to Jincheng Zheng; zhengjincheng.com@163.com
Received 1 July 2013; Revised 19 August 2013; Accepted 27 August 2013
Academic Editor: Hui Zhang
Copyright © 2013 Tao Liu et al. This is an open access article distributed under the Creative Commons Attribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This paper establishes a mathematic model of composite braking in the hydraulic hybrid vehicle and analyzes the constraint con-dition of parallel regenerative braking control algorithm. Based on regenerative braking system character and ECE (EconomicCommission of Europe) regulations, it introduces the control strategy of regenerative braking in parallel hydraulic hybrid vehicle(PHHV). Finally, the paper establishes the backward simulation model of the hydraulic hybrid vehicle in Matlab/simulink andmakes a simulation analysis of the control strategy of regenerative braking.The results show that this strategy can equip the hydraulichybrid vehicle with strong brake energy recovery power in typical urban drive state.
1. Introduction
Regenerative braking is an important technology of thehybrid vehicles that appeals to very strong research interestsall over the world [1–5]. Research on control strategy is oneof most important topics of regenerative braking and can beroughly categorized into two types according to the proposeof research. One is to enhance the braking performance anddriving comfort. The other is to improve the regenerativeefficiency and to save resources. Almost the present researchconcentrates on regenerative braking in many of electricvehicles (EV), hybrid electric vehicles (HEV), and plug-inhybrid electric vehicles. A mass of solutions in regenerativebraking system control have been carried out. For example,Kim et al. [6] and Peng et al. [7] put forward two regenerativebraking strategies based on the fuzzy control to pursue highregenerative efficiency and good braking performance. Thesimulation results indicated that both regenerative brakingcontrol strategies could increase the fuel economy for HEVand improve vehicle stability. Oh et al. [8], Jo et al. [9], Zhanget al. [10], Moreno et al. [11], and others have carried outresearch studies in this field as well. Nevertheless, pieces ofthe literature devoted to hydraulic hybrid vehicle (HHV) arerelatively scarce.Wu et al. [12] proposed a strategy for passen-ger cars based on dividing the accumulator volume into two
parts, one for regeneration and the other for road-decoupling.Hui et al. [13] presented a fuzzy torque control strategy basedon vehicle load changes for real-time controlling the energydistribution in PHHV.Though they proposed amethodologyof braking to improve the fuel economy in a typical urbancycle, the braking characteristicswere not investigated deeply.What is more, the efficiency of brake energy recovery andthe distribution of braking force were not considered andoptimized at all. The design of regenerative braking strategyin HHV remains a problem yet. Compared with electrifiedvehicles, HHV has some advantage, particularly for vehiclescontaining hydraulic equipment on board [14]. For instance,hydraulic accumulator is of higher power density and abilityto accept the high rates and high frequencies of chargingand discharging [15]. Besides, the service life of a hydraulicaccumulator as the storage is more than a battery. Therefore,HHV has a greater potential than electrified vehicles, andthe research on that makes much sense. Generally, thereare two types of hydraulic hybrid systems: parallel hydraulichybrid vehicle (PHHV) and series hydraulic hybrid vehicle(SHHV). PHHV uses a traditional mechanical drive trainwith hydraulic pump/motor unit inline between the trans-mission and axle [16]. The configuration of PHHV is simplerthan that of SHHV and easier to be refitted.Therefore, PHHVoccupies large proportion of HHV at home and abroad.
2 Mathematical Problems in Engineering
However, it is hard for PHHV driven by rear wheel to obtaina good braking stability as well as an effective regenerativeenergy recovery. One reason for this phenomenon is that therear wheel is easy for locking when the hydraulic regenerativebraking force is exerted on the back axle. Therefore, whenthe hydraulic braking force is strong enough, the back-axleutilization adhesion curvesmay surpass the constraint of ECE(Economic Commission of Europe) regulations, resultingin the premature rear lock and decline in the utilizationadhesion coefficient. To cope with this situation, the paperputs forward the control strategy of regenerative braking inthe parallel composite braking system, which consists of theconventional fictional braking system and hydraulic regener-ative braking system.The control strategy is revised accordingto the external character of the parallel composite brakingsystem and ECE regulations. The simulation results demon-strate its effectiveness in improving the brake energy recoveryin typical urban drive state.
2. Configuration of PHHV
This rear-wheel-drive hydraulic hybrid vehicle, shown inFigure 1, consists primarily of an internal combustion engine,a high pressure accumulator, low pressure reservoir, and avariable displacement hydraulic pump/motor unit. The pri-mary power source is the same diesel engine used in theconventional vehicle. The transmission, propeller shaft, andthe differential and driving shaft are the same as those in theconventional vehicle. The hydraulic pump/motor is coupledwith the propeller shaft via a torque coupler [17, 18].The basicparameters of the parallel hydraulic hybrid vehicle studied inthis paper are as shown in Table 1.
During deceleration, the hydraulic pump/motor decel-erates the vehicle while operating as a pump to capture theenergy normally lost to friction brakes in a conventionalvehicle. Also, when the vehicle brake is applied, the hydraulicpump/motor uses the braking energy to charge the hydraulicfluid from a low pressure hydraulic accumulator into a high-pressure accumulator, increasing the pressure of the nitrogengas in the high pressure accumulator. The high pressurehydraulic fluid is used by the hydraulic pump/motor unit togenerate torque during the next vehicle launch and accelera-tion [19–21]. It is designed and sized to capture braking energyfrom normal, moderate braking events and is supplementedby friction brakes for aggressive braking.
Ignoring the vehicle rolling resistance moment, the frontwheel braking force 𝐹𝑓1 and the rear wheel braking force 𝐹𝑓2
are given by the following, respectively:
𝐹𝑓1 =
𝜑 (𝐺𝑏 + 𝑚 (𝑑𝑢/𝑑𝑡) ℎ𝑔 − (𝐶𝐷𝐴𝑢2/21.15) ℎ𝑔)
𝐿,
(1)
𝐹𝑓2 =
𝜑 (𝐺𝑎 − 𝑚 (𝑑𝑢/𝑑𝑡) ℎ𝑔 + (𝐶𝐷𝐴𝑢2/21.15) ℎ𝑔)
𝐿,
(2)
where 𝜑 is the adhesion coefficient between tire and roadsurface, 𝐺 is the vehicle gravity (N), 𝑚 is the vehicle quality
Transmi-ssion
Pump/motor
PumpPlanetary
High pressure accumulator
ECULow pressure accumulator
Engine
Figure 1: Configuration of PHHV.
Table 1: Basic parameters of PHHV.
Name ParameterWheel radius 0.28mMaximum weight 1795 kgComplete vehicle kerb mass 865 kgFinal drive axle ratio 4.129Volume of the hydraulic accumulator 25 LFilling pressure of the hydraulic accumulator 12MPaMaximum working pressure of the hydraulicaccumulator 31MPa
Minimum working pressure of the hydraulicaccumulator 15MPa
Torque coupler gear ratio 1.3Hydraulic pump/motor capacity A4VG56/56mL/r
(kg), 𝑎 is the distance from vehicle center of gravity to frontaxle center line (m), 𝑏 is the distance from vehicle center ofgravity to rear axle center line (m), 𝐿 is wheel base (m), ℎ𝑔 isthe height of the center of gravity (m),𝐶𝐷 is the air resistancecoefficient, 𝐴 is the frontal area (m2), 𝑢 and is the vehiclespeed (m/s).
3. Design of Parallel RegenerativeBraking Control Algorithm
During the composite braking, the brake severity is usuallyset at 0.1∼0.7. After this phase, the regenerative braking forceon the rear wheel, will rise, which will raise the utilizationadhesion coefficient of the rear wheel whereas that of thefront wheel goes down. As a result, the utilization adhesioncoefficient on the rear wheel tends to surpass the constraintof ECE regulations, while the front wheel tends to be safer,with the possibility of lock being lowered in a further way.
In order to ensure the vehicle braking performance,ECE regulations demand the following: when the adhesion
Mathematical Problems in Engineering 3
coefficient 𝜑 is between 0.2 and 0.8, the braking severity is𝑧 ≥ 0.1 + 0.7(𝜑 − 0.2); thus, the following is gained:
𝐹𝑥𝑏2 ≤𝑧 + 0.04
0.7
(𝑎 − 𝑧ℎ𝑔)𝐺
𝐿,
𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2.
(3)
As shown in Figure 2, the maximum rear wheel brakingforce curves are depicted in the wheel braking force distribu-tion diagram, where line OC denotes line 𝛽, over which theideal wheel braking force distribution line 𝐼 lies. The vehiclesynchronization adhesion coefficient is 0.75. The regulationscan be satisfiedwith the ignorance of the regenerative brakingsystem character. Line AB in the figure denotes the compositebraking phasewhen the energy can be recovered to the largestdegree, and OA is the biggest braking force during the pureregenerative braking. In order to prevent the premature lockof rear wheels duringmassive braking (𝑧 > 0.7) of the vehicle,the right boundary line goes down alongwith the line 𝑟wherebrake severity is 0.7, as is shown in Figure 2 as line BC.
In the composite braking phase shown in Figure 2, thebraking force on front and rear wheels is as follows:
𝐹𝑥𝑏2 = 𝐾 (𝐹𝑥𝑏1 + 0.115𝐺) (0.1 < 𝑧 < 𝑧B) ,
𝐹𝑥𝑏2 =
−0.7ℎ𝑔
𝐿 + 0.7ℎ𝑔
𝐹𝑥𝑏1 +0.7𝐺𝑏
𝐿 + 0.7ℎ𝑔
(𝑧B ≤ 𝑧 ≤ 0.7) ,
(4)
where 𝑧B is brake severity corresponding to point B,𝐾 is slopeof line AB.
Here𝐾 = 1.1407, 𝑧B = 0.45. After the revise according topoints A and C, the limit values of braking severity 𝑧 are 0.127and 0.715. The regenerative braking force 𝐹p/m can be gainedby the regenerative braking control algorithm:
𝐹p/m =
{{{{{{{{{
{{{{{{{{{
{
𝑇p/m
𝑟= 𝐺𝑧, 𝑧 ≤ 0.127,
𝐺𝑧 −𝐺 (𝑧 − 0.115𝐾)
(1 + 𝐾) 𝛽, 0.127 < 𝑧 ≤ 𝑧B,
𝐺𝑧 −
𝐺𝑧 (𝐿 + 0.7ℎ𝑔) − 0.7𝐺𝑎
𝐿𝛽, 𝑧B < 𝑧 < 0.715.
(5)
After the concrete parameters of the hydraulic hybrid vehicleare input into the above equations, the relation in conditionsof different brake severity and hydraulic accumulator pres-sure between regenerative braking system character and thealgorithm distribution results is gained, which is depicted inFigure 3. As is shown in the figure, when hydraulic accu-mulator pressure is relatively lower and the brake severity𝑧 ≤ 0.1 and 𝑧 ≥ 0.5, the regenerative braking distributionresult is that the demanded regenerative braking force is lowerthan regenerative braking system character, proving that theregenerative braking power of the system has not been fullyperformed. In the phase of 0.1 < 𝑧 < 0.5, the regenerativebraking power is far from the requirements of the algorithm.Therefore, it is necessary to add character constraint of theregenerative braking system.
0 2000 4000 6000 8000 100000
1000
2000
3000
4000
5000
6000
7000
D
E
B
C
A
The maximum brake force curves according to ECE
Brake force of front wheelFxb1 (N)
Brak
e for
ce o
f fro
nt w
heelFxb
2(N
)
Line I
Line 𝛽
Figure 2: Brake force distribution curves of PHHV.
00.2
0.40.6
0.8
1520
2530
350
1000
2000
3000
4000
Brake severity
Hydraulic pressure (MPa)
Rege
nera
tive b
rake
forc
e (N
)
Figure 3: Relation between regenerative braking system characterand algorithm distribution results.
4. The Parallel Regenerative Braking ControlAlgorithm Based on Regenerative BrakingSystem Character and ECE Regulations
The regenerative braking force is linearly related withhydraulic accumulator pressure. Therefore, the basic thoughtof control algorithm is that before the distribution of eachtime the maximum braking power 𝐹p/m max of the regener-ative braking system is confirmed according to the drivingspeed and hydraulic accumulator pressure; the pure regen-erative braking is adopted when the total braking forcedemand 𝐹bd corresponding to braking severity 𝑧 meets thecondition of 𝐹bd < 𝐹p/m max; otherwise, the compositebraking is adopted. In the process of composite braking, theregenerative braking force will be preferential for use, and thefrictional braking force will supplement the rest.The detailedprocess of algorithm distribution is as follows.
4 Mathematical Problems in Engineering
(1) According to target brake severity, the total brakingforce demand is calculated as 𝐹bd = 𝐺𝑧. The max-imum regenerative braking power 𝐹p/m max at themoment of the hydraulic pump/motor is gained byreferring to the pressure phenomena of the accumu-lator.
(2) If 𝐹p/m max ≥ 𝐹bd, the braking force will be fully pro-vided by the hydraulic pump/motor, when 𝐹p/m = 𝐹bdand both the front wheel frictional braking force 𝐹𝑓
and the rear 𝐹𝑟 will be 0.
(3) If 𝐹p/m max < 𝐹bd, the frictional braking force onfront and rear wheels goes up along with line 𝛽, whenthe regenerative braking force is 𝐹p/m = 𝐹p/m max,the frictional braking force on rear wheels is 𝐹𝑟 =
(1−𝛽)(𝐹bd−𝐹p/m max), and the hydraulic braking forceon front wheels is 𝐹𝑓 = 𝛽(𝐹bd − 𝐹p/m max). Therefore,the regenerative braking force during braking can begained and is shown in Figure 4, while the simultane-ous simulation results of front and rear axle utilizationcoefficients are in Figure 5.
According to Figures 4 and 5, as the algorithm ensuresthe maximum regenerative braking power in the first place,the braking force distribution surpasses the constraint of ECEregulations, resulting in the necessity of adding ECE regu-lations constraints into the algorithm. After the calculation,the relation between the maximum limiting line of ECE reg-ulations to rear wheel braking force and the front-rear forcedistribution line in the phase of the maximum algorithmregenerative braking force is shown in Figure 2.
It can be seen from Figure 2 that line AD which denotesthe basic algorithm distribution is beyond ECE regulations.Thereby, taking point D, for example, the distribution resultsshould be revised onto the point E intersected byECE line andthe corresponding equal-braking-severity line. The detailedrevise algorithm is as follows.
(1) The regenerative braking power 𝐹p/m max should begained from pressure phenomena of hydraulic accumulatorby referring to the target brake severity 𝑧 and the total brakingforce demand 𝐹bd.
(2) If 𝐹p/m max ≥ 𝐹bd, from the following equations
𝐹𝑥𝑏2 = 𝐾 (𝐹𝑥𝑏1 + 0.115𝐺)
0 = 𝐺𝑧 − 𝐹𝑥𝑏1,
(6)
𝐹𝑥𝑏2 = 𝐹𝑥𝑏2A can be gained, where 𝐹𝑥𝑏2A denotes the rearwheel braking force corresponding to point A.
If 𝐹p/m max ≤ 𝐹𝑥𝑏2A, the braking force will be completelyprovided by regenerative braking, when the regenerativebraking moment is 𝑇p/m = 𝐹bd/𝑟 and the front wheel fric-tional braking force 𝐹𝑓 and the rear 𝐹𝑟 are both 0, whichshould be revised otherwise. The detail is as follows.
If 0 < 𝑧 ≤ 0.127, the regenerative braking moment is𝑇p/m = 𝐹bd/𝑟 and both the front frictional braking force 𝐹𝑓
and the rear 𝐹𝑟 are 0.
1520
2530
35
00.2
0.40.6
0.80
1000
2000
3000
4000
Hydraulic pressure (MPa)Brake severity
Rege
nera
tive b
rake
forc
e (N
)
Figure 4: The results of the algorithm allocation based on the con-strained regenerative braking system.
If 0.127 < 𝑧 ≤ 0.2,
𝐹𝑥𝑏2 = 𝐾 (𝐹𝑥𝑏1 + 0.115𝐺) ,
𝐹𝑓 = 𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
𝐹𝑓 =𝛽
1 − 𝛽𝐹𝑟,
𝐹𝑚 = 𝐹bd − 𝐹𝑟 − 𝐹𝑓.
(7)
If 0.2 < 𝑧 ≤ 0.45,
𝐹𝑥𝑏2 =𝑧 + 0.04
0.7
(𝑎 − 𝑧ℎ𝑔)𝐺
𝐿,
𝐹𝑓 = 𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
𝐹𝑓 =𝛽
1 − 𝛽𝐹𝑟,
𝐹𝑚 = 𝐹bd − 𝐹𝑟 − 𝐹𝑓.
(8)
If 0.45 < 𝑧 ≤ 0.715,
𝐹𝑥𝑏2 = −
0.7ℎ𝑔
𝐿 + 0.7ℎ𝑔
𝐹𝑥𝑏1 +0.7𝐺𝑎
𝐿 + 0.7ℎ𝑔
,
𝐹𝑓 = 𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
𝐹𝑓 =𝛽
1 − 𝛽𝐹𝑟,
𝐹𝑚 = 𝐹bd − 𝐹𝑟 − 𝐹𝑓.
(9)
(3) If 𝐹p/m max < 𝐹bd, the predistributed front-rear wheel fric-tional braking force rises along line 𝛽. The regenerative brak-ing force is 𝐹p/m = 𝐹p/m max, while the rear wheel frictionalbraking force is 𝐹𝑟 = (1 − 𝛽)(𝐹bd − 𝐹p/m max) and the front is𝐹𝑓 = 𝛽(𝐹bd − 𝐹p/m max).
If 0 < 𝑧 ≤ 0.127, the regenerative braking force is 𝐹𝑚 =
𝐹max, while the rear wheel frictional braking force is 𝐹𝑟 = (1−
𝛽)(𝐹bd − 𝐹p/m max) and the front is 𝐹𝑓 = 𝛽(𝐹bd − 𝐹p/m max).
Mathematical Problems in Engineering 5
0 0.1 0.2 0.3 0.4 0.5 0.6 0.70
0.10.20.30.40.50.60.70.80.9
1
Brake severity
Util
izat
ion
adhe
sion
coeffi
cien
t
Line ECE
Utilization adhesioncoefficient of the
Utilization adhesion
front axle at 15 Mpa
coefficient of the rearaxle at 15 Mpa
Utilization adhesioncoefficient of the
Utilization adhesioncoefficient of the rear
axle at 31 Mpa
front axle at 31 Mpa
f = z
(a) Full load
Brake severity
Util
izat
ion
adhe
sion
coeffi
cien
t
Line ECE
Utilization adhesion coefficient of the
front axle at 15 Mpa
Utilization adhesioncoefficient of the rear
axle at 15 Mpa
Utilization adhesioncoefficient of the
front axle at 31 Mpa
Utilization adhesioncoefficient of the rear
axle at 31 Mpa
0 0.1 0.2 0.3 0.4 0.5 0.6 0.70
0.10.20.30.40.50.60.70.80.9
1
𝜑 = z
(b) Empty load
Figure 5: Simulation results of front and rear axle utilization coefficients.
1520
2530
35
00.2
0.40.6
0.80
1000
2000
3000
4000
Accumulator pressure (MPa)Brake severity
Rege
nera
tive b
rake
forc
e (N
)
Figure 6:The results of braking force distribution revised accordingto ECE regulations.
If 0.127 < 𝑧 ≤ 0.2, from the equations
𝐹𝑥𝑏2 = 𝐾 (𝐹𝑥𝑏1 + 0.115𝐺) ,
𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
(10)
𝐹𝑥𝑏1 = 𝐹𝑥𝑏1E can be gained, where 𝐹𝑥𝑏1E denotes the frontwheel braking force corresponding to point E. If the predis-tribution result is𝐹𝑓 > 𝐹𝑥𝑏1E, the revise is not necessary, whilethis is needed otherwise. The revise results are as follows
𝐹𝑥𝑏2 = 𝐾 (𝐹𝑥𝑏1 + 0.115𝐺) ,
𝐹𝑓 = 𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
𝐹𝑓 =𝛽
1 − 𝛽𝐹𝑟,
𝐹p/m = 𝐹bd − 𝐹𝑟 − 𝐹𝑓.
(11)
If 0.2 < 𝑧 ≤ 0.45, from the equations
𝐹𝑥𝑏2 =𝑧 + 0.04
0.7
(𝑎 − 𝑧ℎ𝑔)𝐺
𝐿,
𝐹𝑓 = 𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
(12)
𝐹𝑥𝑏1 = 𝐹𝑥𝑏1E can be gained, where 𝐹𝑥𝑏1E denotes the frontwheel braking force corresponding to point E. If the predis-tribution result is𝐹𝑓 > 𝐹𝑥𝑏1E, the revise is not necessary, whilethis is needed otherwise. The revise results are as follows
𝐹𝑥𝑏2 =𝑧 + 0.04
0.7
(𝑎 − 𝑧ℎ𝑔)𝐺
𝐿,
𝐹𝑓 = 𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
𝐹𝑓 =𝛽
1 − 𝛽𝐹𝑟,
𝐹p/m = 𝐹bd − 𝐹𝑟 − 𝐹𝑓.
(13)
If 0.45 < 𝑧 ≤ 0.715, from the equations
𝐹𝑥𝑏2 =
−0.7ℎ𝑔
𝐿 + 0.7ℎ𝑔
𝐹𝑥𝑏1 +0.7𝐺𝑎
𝐿 + 0.7ℎ𝑔
,
𝐹𝑓 = 𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
(14)
𝐹𝑥𝑏1 = 𝐹𝑥𝑏1E can be gained, where 𝐹𝑥𝑏1E denotes the frontwheel braking force corresponding to point E. If the predis-tribution result is𝐹𝑓 > 𝐹𝑥𝑏1E, the revise is not necessary, whilethis is needed otherwise. The revise results are as follows
𝐹𝑥𝑏2 =
−0.7ℎ𝑔
𝐿 + 0.7ℎ𝑔
𝐹𝑥𝑏1 +0.7𝐺𝑎
𝐿 + 0.7ℎ𝑔
,
𝐹𝑓 = 𝐹𝑥𝑏1 = 𝐺𝑧 − 𝐹𝑥𝑏2,
𝐹𝑓 =𝛽
1 − 𝛽𝐹𝑟,
𝐹p/m = 𝐹bd − 𝐹𝑟 − 𝐹𝑓.
(15)
6 Mathematical Problems in Engineering
Brake severity
Util
izat
ion
adhe
sion
coeffi
cien
t
Line ECE
Utilization adhesion coefficient of the
front axle at 15 Mpa
Utilization adhesioncoefficient of the rear
axle at 15 Mpa
Utilization adhesioncoefficient of the
front axle at 31 Mpa
Utilization adhesioncoefficient of the rear
axle at 31 Mpa
𝜑 = z
0 0.1 0.2 0.3 0.4 0.5 0.6 0.70
0.10.20.30.40.50.60.70.80.9
1
(a) Full load
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.10.20.30.40.50.60.70.80.9
0
1
Brake severity
Util
izat
ion
adhe
sion
coeffi
cien
t
Line ECE
Utilization adhesioncoefficient of the
front axle at 31 Mpa
Utilization adhesioncoefficient of the rear
axle at 15Mpa
Utilization adhesion coefficient of the
front axle at 15 Mpa
Utilization adhesioncoefficient of the rear
axle at 31 Mpa
f = z
(b) Empty load
Figure 7: Simulation results of revised front and rear axle utilization coefficients.
Adhesion coefficient
Vehi
cle ad
hesio
n effi
cien
cy
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.10.20.30.40.50.60.70.80.9
0
1
Figure 8:The vehicle adhesion efficiency based on parallel regener-ative braking.
The results of braking force distribution revised according toECE regulations are shown in Figure 6, and the utilizationadhesion coefficient curves are shown in Figure 7.
The comparisons between Figures 4 and 6 as well asFigures 5 and 7 show that the revised zone is relatively largeand the distribution results after revise can satisfy the re-quirements of both regenerative braking system and ECEregulations.
According to Figure 2 which tells the distribution phe-nomena, on the condition of the remaining braking forceratio 𝛽, ECE regulation limits can be easily exceeded if theparallel regenerative braking control algorithmwithout reviseby ECE is adopted, aiming to fully perform the regener-ative braking power. Although the braking force distribu-tion results revised according to ECE regulations meet therequirement of the regulations, the braking energy recoveryefficiency is affected, however, resulting in the necessity ofrematch to the braking force ratio 𝛽 to improve the safety andenergy recovery efficiency of hydraulic hybrid vehicles.
According to Figure 7, in order to recover the brakingenergy to the largest degree, the rear axle will be preferentiallyexerted on regenerative braking force; thus, the utilization
adhesion coefficient on the rear axle is above that of the front.Therefore, the rear wheels will lock every time before thefront ones, which is a dangerous condition. Hence, the hybridvehicle driven by rear wheels must be equipped with ABS(antilock brake system), which controls the performance ofregenerative braking system. At the same time, however, thevehicle adhesion efficiency should satisfy the requirement ofregulations of 𝜀 ≥ 0.75.
The vehicle adhesion efficiency when braking is depictedin Figure 8. When the vehicle brakes on the road withextralow adhesion coefficient (below 0.3 in the figure), theadhesion efficiency will be 𝜀 < 0.75. Therefore, if the roadadhesion coefficient is lower than 0.3, the parallel compositebraking system will checkout the information about the roadadhesion phenomenon though ABS and the regenerativebraking system controller, and then it stops exerting regen-erative braking force at the right time.
5. Simulation Research
Vehicle control model is the core of control strategy. Basedon the requirement of driving cycle, the total torques aredistributed among engine, hydraulic accumulator, hydraulicpump/motor, and the friction brake system reasonably. Vehi-cle control model consists of regenerative braking system,energy release system, and active stamping system, as shownin Figure 9.
Based on the algorithm above, the model of brakingforce distribution on hydraulic hybrid vehicles is set up inMatlab/Simulink and shown in Figure 10.
In order to verify the rationality and validity of theregenerative braking strategy discussed in this chapter, theparallel regenerative braking control strategy is adopted, and1015, NYCC, and UDDS drive states are chosen to makethe simulation study of brake energy recovery. After theroad being set with high adhesion coefficient, the simulationresults are achieved and shown in Table 2. Meanwhile theresults of the evaluation of driving cycles with strategy of theADVISOR in [22] are cited and shown in Table 3.
According to Table 2, the control strategy of regenerativebraking in the hydraulic hybrid vehicle discussed in this
Mathematical Problems in Engineering 7
2
Required torque
System pressure
Pump displacement
3
4
1
5
Regenera-tive
braking
Energy release
Activestamp-
ing
+++
0
2
1
0
Shaft speed
Engine economic torque
Mode
3
Mode
Pump torque
Shaft speed
Shaft torque
Torq-ue
Judg-ment
60
Torquedecomp-osition
<0
≥0
Figure 9: Top-level diagram of vehicle control model.
Demand brake force
Pump speed
Peak pressure
Brake severity
−+
−+
ß −+
×++
OR 0
1
+−−
2
3
Frictional brake force of the front axle
Frictional brake force of the rear axle
Regenerative brake force
Maximum brake force of the rear axle
Brake force of the front axle
Brake force of the rear axle
cSystem pressure
0
0
Maximum pump speed
Pump displacement
≥
(1 − ß)/ß
≤
≤
Figure 10: Model of braking force distribution of parallel regenerative braking.
paper can achieve the brake energy recovery to the largestdegree based on the brake security.The brake energy recoveryefficiency in 1015, NYCC, and UDDS is, respectively, 73.5%75.25%, and 60.60%.
Compare the results in Table 2 with those in Table 3; it isnot hard to find that the control strategy of regenerative brak-ing in the hydraulic hybrid vehicle discussed in this paper canachieve more brake energy recovery than the strategy of theADVISOR cited in [22].
6. Conclusions
Based on the higher power density and lower energy densityof the hydraulic accumulator as well as the characteristics ofthe urban state, this paper puts forward the control algorithmof parallel composite braking in the hydraulic hybrid vehicledriven by rear wheels. By means of revise, the compositebraking was controlled just within the requirements of ECEregulations. Therefore, based on the ensured brake security,
8 Mathematical Problems in Engineering
Table 2: The results of brake energy recovery rate in different drive states with the proposed strategy.
Drive state Average accelerationaavg (m⋅s−2)
Brake severity𝑧 ≤ 0.1 (%)
Brake energy𝐸𝑟 (kWh)
Brake energy recovery rate𝜀𝑟 (%)
1015 0.57/−0.65 96.2 0.2256 73.5NYCC 0.62/−0.61 75.5 0.04 75.25UDDS 0.51/−0.58 74.5 2.731 60.60
Table 3: The results of the evaluation of driving cycles with strategy of the ADVISOR.
Drive state Traveling distance(Km)
Brake energy(kJ)
Regenerative braking efficient(kJ)
Brake energy recovery rate(%)
1015 4.2 660 367 56NYCC 1.9 614 302 49UDDS 12 1856 1017 55
the algorithm designed can enlarge the regenerative brakingratio to the utmost in the phase of composite braking,improving the brake energy recovery power of the vehicle atthe end.
Acknowledgments
This work was supported by National Natural Science Foun-dation of China and Natural Science Foundation of Shan-dong Province under Contracts no. 50875054 and no.ZR2009FL002.
References
[1] W.Gunselman, “Technologies for increased energy efficiency inrailway systems,” in Proceedings of the 11th European Conferenceon Power Electronics and Applications, pp. 1–10, 2005.
[2] K. Son, S. Noh, K. Kwon, J. Choi, and E. K. Lee, “Line voltageregulation of urban transit systems using supercapacitors,” inProceedings of the IEEE 6th International Power Electronics andMotion Control Conference (IPEMC ’09), pp. 933–938, May2009.
[3] K. Matsuda, H. Ko, and M. Miyatake, “Train operation min-imizing energy consumption in dc electric railway with on-board energy storage device,” in Power Supply, Energy Man-agement and Catenary Problems Part A, pp. 45–54, WIT Press,Southampton, UK, 2010.
[4] T. Konishi, H. Morimoto, T. Aihara, and M. Tsutakawa, “Fixedenergy storage technology applied for DC Electrified railway,”IEEJ Transactions on Electrical and Electronic Engineering, vol.5, no. 3, pp. 270–277, 2010.
[5] M. Ogasa, “Application of energy storage technologies for elec-tric railway vehicles-examples with hybrid electric railway vehi-cles,” IEEJ Transactions on Electrical and Electronic Engineering,vol. 5, no. 3, pp. 304–311, 2010.
[6] D. Kim, S. Hwang, and H. Kim, “Vehicle stability enhancementof four-wheel-drive hybrid electric vehicle using rear motorcontrol,” IEEE Transactions on Vehicular Technology, vol. 57, no.2, pp. 727–735, 2008.
[7] D. Peng, Y. Zhang, C. L. Yin, and J. W. Zhang, “Combinedcontrol of a regenerative braking and antilock braking systemfor hybrid electric vehicles,” International Journal of AutomotiveTechnology, vol. 9, no. 6, pp. 749–757, 2008.
[8] K. Oh, D. Kim, T. Kim, C. Kim, and H. Kim, “Operation algo-rithm for a parallel hybrid electric vehicle with a relatively smallelectric motor,” KSME International Journal, vol. 18, no. 1, pp.30–36, 2004.
[9] C. Jo, J. Ko, H. Yeo, T. Yeo, S. Hwang, and H. Kim, “Cooper-ative regenerative braking control algorithm for an automatic-transmission-based hybrid electric vehicle during a downshift,”Proceedings of the Institution of Mechanical Engineers, Part D:Journal of Automobile Engineering, vol. 226, no. 4, pp. 457–467,2012.
[10] J. Zhang, C. Lv, J. Gou, and D. Kong, “Cooperative control ofregenerative braking and hydraulic braking of an electrifiedpassenger car,” Proceedings of the Institution of Mechanical Engi-neers, Part D: Journal of Automobile Engineering, vol. 226, no.10, pp. 1289–1302, 2012.
[11] J. Moreno, M. E. Ortuzar, and J. W. Dixon, “Energy-manage-ment system for a hybrid electric vehicle, using ultracapacitorsand neural networks,” IEEE Transactions on Industrial Electron-ics, vol. 53, no. 2, pp. 614–623, 2006.
[12] P.Wu,N. Luo, F. J. Fronczak, andN.H. Beachley, “Fuel economyand operating characteristics of a hydropneumatic energystorage automobile,” SAE Paper 851678, 1985.
[13] S. Hui, J. Ji-hai, and W. Xin, “Torque control strategy for aparallel hydraulic hybrid vehicle,” Journal of Terramechanics,vol. 46, no. 6, pp. 259–265, 2009.
[14] A. Taghavipour, M. S. Foumani, and M. Boroushaki, “Imple-mentation of an optimal control strategy for a hydraulic hybridvehicle using CMAC and RBF networks,” Scientia Iranica, vol.19, no. 2, pp. 327–334, 2012.
[15] S. Hui, “Multi-objective optimization for hydraulic hybrid vehi-cle based on adaptive simulated annealing genetic algorithm,”Engineering Applications of Artificial Intelligence, vol. 23, no. 1,pp. 27–33, 2010.
[16] R. Ramakrishnan, S. S. Hiremath, andM. Singaperumal, “Theo-retical investigations on the effect of system parameters in serieshydraulic hybrid systemwith hydrostatic regenerative braking,”Journal of Mechanical Science and Technology, vol. 26, no. 5, pp.1321–1331, 2012.
[17] R. P. Kepner, “Hydraulic power assist—a demonstration ofhydraulic hybrid vehicle regenerative braking in a road vehicleapplication,” SAE Paper 2002-01-3128, 2002.
[18] T. Liu, J. Jiang, and H. Sun, “Investigation to simulation ofregenerative braking for parallel hydraulic hybrid vehicles,”
Mathematical Problems in Engineering 9
in Proceedings of the International Conference on MeasuringTechnology and Mechatronics Automation (ICMTMA ’09), pp.242–245, April 2009.
[19] Y. J. Kim and Z. Filipi, “Simulation study of a series hydraulichybrid propulsion system for a light truck,” SAE Paper 2007-01-4151, 2007.
[20] R. P. Kepner, “Hydraulic power assist—a demonstration ofhydraulic hybrid vehicle regenerative braking in a road vehicleapplication,” SAE Paper 2002-01-3128.
[21] M. Paul and S. Jacek, “Development and simulation of ahydraulic-hybrid powertrain for use in commercial heavyvehicles,” SAE Paper 2003-01-3370.
[22] L. Chu, M. Shang, Y. Fang, J. Guo, and F. Zhou, “Braking forcedistribution strategy for HEV based on braking strength,” inProceedings of the International Conference on Measuring Tech-nology and Mechatronics Automation (ICMTMA ’10), pp. 759–764, March 2010.
Submit your manuscripts athttp://www.hindawi.com
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttp://www.hindawi.com
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Journal of
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
CombinatoricsHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
International Journal of
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
The Scientific World JournalHindawi Publishing Corporation http://www.hindawi.com Volume 2014
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttp://www.hindawi.com
Volume 2014 Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014
Stochastic AnalysisInternational Journal of
top related